The present invention relates generally to the field of mousepads and, more particularly, to the field of mousepads for optical mice.
Most computers now have an input device that controls the movement of a cursor on a computer screen. Examples of such devices include trackballs, joysticks, and mice. A common form of the mouse is a mechanical mouse; it has a small ball on its underside in contact with the surface upon which the mouse rests. When the mouse is moved, the ball rolls and activates sensors in the mouse that translate the rolling of the ball into movement of the cursor on the computer screen. Another kind of mouse is an optical mouse. The optical mouse has an optical sensor that scans a surface and acquires a series of images of the surface. The optical mouse determines its own position relative to the surface by comparing the differences between consecutive images.
A typical optical mouse illuminates the surface it is scanning, generating shadows and reflections used by the optical sensor to acquire a good image. Depending on the surface type, the amount of light needed can vary. For instance, a dark surface absorbs light, requiring more light to adequately illuminate the surface in order for the optical sensor to acquire a usable image. The more light used by the optical mouse, however, the more power it consumes. This is a problem for low-power applications such as battery operated cordless mice, or for laptop computer users.
The performance of the optical mouse also depends on the surface that it scans. If a surface is too homogeneous, the images acquired by the optical sensor while the optical mouse is moving will all be very similar, perhaps even identical. Since the optical mouse depends on differences between images to determine its position relative to the surface, similar images trick it into thinking that it has not changed position, when in fact it has. It is therefore important that the surface has enough distinguishing characteristics to eliminate such confusion.
A surface having specular regions shaped to reflect incident light towards the optical sensor provides an ideal surface to be scanned by the optical mouse. When light is shined upon the surface, the reflections off of the specular regions appear as bright white points in the image acquired by the optical sensor, which gives the optical sensor the distinguishing characteristics it needs to differentiate between images. Since the specular regions reflect light so well, less light is needed to obtain an image, so power is conserved. The surface itself should either reflect light away from the optical sensor, or at least scatter light, so that it appears in the image to the optical sensor as a dark background, providing contrast to the light reflecting off of the specular regions.
In accordance with an illustrated preferred embodiment of the present invention, the specular regions are depressions that are either made of, or are coated with, a specular material, and are shaped to reflect incident light toward the optical sensor. The surface is made of or coated with a specular material as well, or a material that scatters light. The reflections off of the depressions give the surface its distinguishing characteristics so the mouse is able to differentiate between images as it moves. Additionally, the brightness of the reflections helps the mouse conserve power.
In another embodiment of the present invention, a surface is dotted with protrusions that reflect incident light toward the optical sensor. The protrusions are also either made of, or are coated with, a specular material, and perform the same function as the depressions.
In a third embodiment of the present invention, the surface, whether dotted with depressions or protrusions, is coated with an optically transparent material that protects the surface from contamination or damage. The optically transparent material still allows light to pass through, but prevents the optical mouse from eroding away the specular regions as it traverses over the surface.
In a fourth embodiment of the present invention, the surface has contrasting regions of two colors: one light, one dark. The lighter color is used in the background of the surface to minimize power consumption. The darker colored regions provide distinguishing characteristics on the surface for the optical sensor. Unlike the depressions and protrusions, however, the dark-colored regions do not reflect light well. As a result, when the optical sensor scans the surface, the dark colored regions appear to it as dark spots against a lighter background. This embodiment does not conserve as much power as the embodiments with the specular regions, but a colored surface may be easier to manufacture than a surface with depressions or protrusions.
Further features and advantages of the present invention, as well as the structure and operation of preferred embodiments of the present invention, are described in detail below with reference to the accompanying exemplary drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.